Multifunction devices having a facsimile function, printer function, scan function, and copy function are well known in the art. In recent years, smaller and less expensive multifunction devices have become widespread.
Some of the multifunction devices are required to compress image data in a prescribed compression format and expand data compressed according to the prescribed compression format. These data compression and expansion processes are essential in particular for multifunction devices having a color scan function, color facsimile function, and PC print function, as the volume of color image data handled by these devices can be considerably large. In recent years, the JPEG format has become commonly used as color image data for images taken by digital cameras, scanned by color facsimile devices, and saved with PC applications. Therefore, multifunction devices that process digital images are required to provide sufficient support for data in the JPEG format.
An image-forming device disclosed in Japanese patent application publication No. HEI-8-194812 is provided with a special JPEG processing hardware for performing JPEG compression processes. Since this hardware is dedicated to JPEG compression and expansion processes, the hardware is advantageous in its ability to perform such processes more quickly than software processes performed by a common CPU.
However, since multifunction devices have multiple functions that require JPEG compression and expansion processes, when one function is using the JPEG processing hardware, another function cannot use the JPEG compression or expansion hardware, requiring excess processing time for the another function to complete the process. A process delay caused by the JPEG compression/expansion process of the another function being completely put on hold until the one function completes a JPEG compression/expansion process can make the user feel uneasy.
This problem can be resolved by providing a plurality of JPEG processing hardware sets, enabling a plurality of processes to be performed in parallel. However, the cost of the JPEG processing hardware itself and the cost of circuit boards and circuit configurations required to connect the plurality of JPEG processing hardware sets to other configurations is excessive and, thus, mounting a plurality of JPEG processing hardware sets in a multifunction device is not desirable when the producing cost of the multifunction device tries to be reduced. Further, since it is necessary to mount the JPEG processing hardware and wiring patterns required to connect the JPEG processing hardware to other configurations on a circuit board, this configuration is not suitable for achieving a more compact multifunction device.